1. Field of the Invention
The present invention relates to an etching apparatus, and more particularly, to an apparatus for etching glass substrate uniformly.
2. Discussion of the Related Art
CRT (cathode ray tube) display devices applicable to television or personal computers, for example, have large size screens. Since a luminous material-coated screen should be spaced apart a predetermined distance from an electron gun, there is a problem that the total volume of the display device becomes large. Thus, such CRTs cannot be applied to small size and low power consumption electronics such as a wall-mounted television, portable television, and notebook computers.
For small size and low power consumption, flat panel display devices such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), ELD (Electroluminescent Display), and VFD (Vacuum Fluorescent Display) have been introduced. In these flat panel display devices, the LCD has been most actively researched recently because of good picture quality and low power consumption in spite of various disadvantages. Although portable televisions and notebook computers having the LCD have been marketed, there are various problems yet to be solved. Because televisions and computers have become portable electronics, the reduction of the size and weight is one of the goals in the LCD research.
There are various methods to reduce the size and weight of the LCD. It is, however, difficult to reduce the number of the essential elements of the LCD. In addition, the weight and size of the essential elements are so small that the weight and size of the essential elements hardly can be reduced further. Fortunately, a glass substrate, which is one of the most basic element of the LCD, may be reduced in weight. Specially, the weight reduction of the glass substrate is very important because it makes up a large portion of the total weight of the LCD.
To reduce the weight of the glass substrate, the substrate has to be thinner. The glass processing is, however, very difficult technically because the processed thin glass can be easily damaged and the surface becomes rough after the process if it is not properly done.
Conventionally, the most useful method of reducing the weight of the glass substrate is to etch the surface of the glass substrate by soaking the substrate in a container having an etchant. In this method, however, the substrate is often not etched uniformly because of the non-uniform surface of the substrate. Further, the impurities generated during the etching process are attached to the surface of the substrate, so that the surface becomes even rougher.
To solve the aforementioned problems, the substrate is set up in the container having the etchant and then bubbles are generated to the surface of the substrate through a porous plate to remove the impurities attached on the surface of the substrate and a fresh etchant is applied to the surface of the substrate. In this method, however, since the bubbles having different sizes are applied on the upper portion and lower portion of the substrate, there is a thickness difference between the upper portion and lower portion. As a result, the substrate is still easily damaged even by light force during the LCD process because of the non-uniformity of the substrate. Further, the substrate has to be soaked for a long period, for example, scores of minutes, to etch the substrate sufficiently. Thus, the processing cost is increased in this method.